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Articles 3691 - 3720 of 3783

Full-Text Articles in Physical Sciences and Mathematics

Fluorine, Richard H. Langley, Larry Welch Jan 1983

Fluorine, Richard H. Langley, Larry Welch

Faculty Publications

Considering the long time in which fluorine compounds have been used it seems rather surprising that it was not isolated as an element until 1886. This long delay was not due to lack of effort, but to the reactivity of fluorine and the hazards of working with it and many of its compounds.

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Sources Of Nosocomial Infections In Immunocompromised Patients (Letter), B. Burt Gerstman Jan 1983

Sources Of Nosocomial Infections In Immunocompromised Patients (Letter), B. Burt Gerstman

Faculty Publications

No abstract provided.

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Computing As A Part Of A P.H.D Students Education: A Position Paper, Andrew D. Bailey, Rayman D. Meservy Jan 1983

Computing As A Part Of A P.H.D Students Education: A Position Paper, Andrew D. Bailey, Rayman D. Meservy

Faculty Publications

The skills and abilities associated with computer literacy are becoming required tools for accounting Ph.D. students. Not only are new doctoral students entering Ph.D. programs with better skills, they are also applying these skills more on a day to day basis. This paper presents a brief discussion of a number of issues associated with computer use and computer literacy in general. The paper also presents several aspects of the Ph.D. program at the University of Minnesota and how computers are affecting the program.

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High-Temperature Battery Calorimeter, L. D. Hansen, R. H. Hart, D. M. Chen, H. F. Gibbard Apr 1982

High-Temperature Battery Calorimeter, L. D. Hansen, R. H. Hart, D. M. Chen, H. F. Gibbard

Faculty Publications

A battery calorimeter was built for the measurement of thermal energy generation of high-temperature lithium–aluminum/iron sulfide battery cells, which are under development for electric vehicle propulsion and other energy storage applications. The calorimeter was designed with a temperature range of 400˚–500˚C, a detection limit of 1 mW, and an upper limit of heat flow of 50 W. The results of measurements on 200-Ah LiAl/FeS cells were in excellent agreement with the predictions of thermodynamic calculations based on precise measurements of the total cell polarization and the temperature coefficient of the emf. Details of the construction and operation principles of this …

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A Hidden-Line Algorithm For Hyperspace, Robert P. Burton, David R. Smith Feb 1982

A Hidden-Line Algorithm For Hyperspace, Robert P. Burton, David R. Smith

Faculty Publications

An object-space hidden-line algorithm for higher-dimensional scenes has been designed and implemented. Scenes consist of convex hulls of any dimension, each of which is compared against the edges of all convex hulls not eliminated by a hyperdimensional clipper, a depth test after sorting and a minimax text. Hidden and visible elements are determined in accordance with the dimensionality of the selected viewing hyperspace. When shape alone is the attribute of interest, hidden-line elimination need be performed only in that hyperspace. The algorithm is of value in the production of shadows of hyperdimensional models, including but not limited to four-dimensional space-time …

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Conductance In Restricted-Dimensionality Accumulation Layers, A. B. Fowler, A. Hartstein, Richard A. Webb Jan 1982

Conductance In Restricted-Dimensionality Accumulation Layers, A. B. Fowler, A. Hartstein, Richard A. Webb

Faculty Publications

Conductance has been studied in metal-oxide-silicon field-effect transistor accumulation-layer samples in which it is possible to constrict the channel to small dimensions both perpendicular to the surface and perpendicular to the channel. A temperature-dependent conductance σ=σ0exp[-(T0/T)n] is observed, where n=1/2 for small channel widths and n=1/3 for larger channel widths. It is believed that this behavior arises from a transition from one-dimensional to two-dimensional variable-range hopping in the sample.

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Classroom Demonstration Of Sunspots, Thomas O. Callaway, Harry D. Downing, Glen T. Clayton Jan 1982

Classroom Demonstration Of Sunspots, Thomas O. Callaway, Harry D. Downing, Glen T. Clayton

Faculty Publications

No abstract provided.

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Physical Science Workshop Course For Elementary Teachers, Glen T. Clayton, Harry D. Downing, Thomas O. Callaway Jan 1982

Physical Science Workshop Course For Elementary Teachers, Glen T. Clayton, Harry D. Downing, Thomas O. Callaway

Faculty Publications

Science for elementary school grades K-6 varies somewhat in content from one textbook series to another, but it is fairly common that 40-60% of the material covered is directly related to physics. These texts suggest that certain learning activities such as experiments, demonstrations, and observations be carried out by the teacher and the class. Often the apparatus for a learning activity is to be constructed from simple, readily available materials. The typical elementary school teacher has had little experience in performing experiments and is often frustrated in his/her attempts at carrying out the suggested learning activity. To meet this need …

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Bond Hybrids And The Structures Of The Lanthanide Metals [Abstract], Richard H. Langley Jan 1982

Bond Hybrids And The Structures Of The Lanthanide Metals [Abstract], Richard H. Langley

Faculty Publications

The ideas developed by Altmann, Coulson, and Hume-Rothery to relate bond hybrids to metal structures are extended to include treatment of the f orbitals. A discussion of the possible hybrids along with their application to the lanthanide metals will be considered.

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Some Comments On The Erdos-Renyl Law And A Theorem Of Shepp, James Lynch Jan 1982

Some Comments On The Erdos-Renyl Law And A Theorem Of Shepp, James Lynch

Faculty Publications

We show that the finiteness of the moment generating function is necessary for the finiteness of the lim sup of the moving averages considered by Shepp (1964). This also implies that the same must be true for the Erdos-Renyi law of large numbers.

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Metrizability And The Frechet-Urysohn Property In Topological Groups, Peter J. Nyikos Dec 1981

Metrizability And The Frechet-Urysohn Property In Topological Groups, Peter J. Nyikos

Faculty Publications

A question of Arhangel'skii, whether weakly first countable topological groups are metrizable, is answered in two ways: if the Hausdorff axiom is assumed, the answer is yes, but in general a weakly first countable topological group need not be pseudometrizable. The former result is obtained as a corollary of a more general sufficient condition for a sequential group to be Fr&chet-Urysohn. A general necessary and sufficient condition for a sequential group to be Frechet-Urysohn is given, and a number of questions are raised. Examples are given to show in what respect the theorems of the paper are the "best possible".

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Macroscopic Quantum Tunneling In 1-Μm Nb Josephson Junctions, Richard F. Voss, Richard A. Webb Jul 1981

Macroscopic Quantum Tunneling In 1-Μm Nb Josephson Junctions, Richard F. Voss, Richard A. Webb

Faculty Publications

The probability distributions for switching out of the superconducting state of low-cur-rent-density 1-μm Nb Josephson junctions with capacitance ≈ 0.1 pF have been measured as a function of temperature T down to 3 mK. Below 100 mK the distribution widths become independent of T. The results are in excellent agreement with predictions for the quantum tunneling of the (macroscopic) junction phase that include the reduction of tunneling rates due to dissipation.

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Landau Free Energy Form At The F Point Of The Roverline3 Structure, Dorian M. Hatch, Daniel L. Decker Feb 1981

Landau Free Energy Form At The F Point Of The Roverline3 Structure, Dorian M. Hatch, Daniel L. Decker

Faculty Publications

A free energy form compatible with the F point of the trigonal D63d(Roverline3c) symmetry is constructed. It is a function of the order parameter, elastic strain, and the stress. The resulting free energy exhibits a close formalistic analogy to the stressed cubic perovskite structures and their associated multicriticality.

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A White Ammonia Fountain, John T. Moore Jan 1981

A White Ammonia Fountain, John T. Moore

Faculty Publications

Red, white, and blue ammonia fountains are a stunning addition to chemistry magic shows.

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Classical Demonstrations Performed To A New Beat, John T. Moore Jan 1981

Classical Demonstrations Performed To A New Beat, John T. Moore

Faculty Publications

Music can help fill the gaps in time during demonstrations and make demonstrations more exciting.

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Wave Demonstration Device, Glen T. Clayton, Harry D. Downing, Thomas O. Callaway Jan 1981

Wave Demonstration Device, Glen T. Clayton, Harry D. Downing, Thomas O. Callaway

Faculty Publications

Students often have difficulty gaining an understanding of wave motion without effective demonstrations being performed in the lecture. Many excellent approaches utilizing ripple tanks, waves on a spring, chain, rope, etc., are customarily employed. Perhaps the most well-known device for demonstrating many of the effects of wave motion is the shive or bell wave motion machine.1 The purpose of the present note is to describe a simple, inexpensive device which can be easily constructed by a teacher or student and can be used to demonstrate many of the properties of wave motion.

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A Rolling Laboratory Platform For The Mobility Handicapped, John T. Moore Jan 1981

A Rolling Laboratory Platform For The Mobility Handicapped, John T. Moore

Faculty Publications

Portable laboratory stations designed for use by the mobility handicapped are available, but the expense of these precludes their use by many institutions. These authors share a more affordable solution.

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Federal Protection Of Unique Environmental Interests: Endangered And Threatened Species, Ronald H. Rosenberg Jan 1980

Federal Protection Of Unique Environmental Interests: Endangered And Threatened Species, Ronald H. Rosenberg

Faculty Publications

Endangered species protection has long been favored by many Americans, who watched regretfully as the numbers of American eagles, buffaloes and other species dwindled toward extinction. Only recently, however, has species protection become a matter of public controversy, subsumed in the more general "development v. environment" debate. In this Article, Professor Rosenberg surveys the federal government's role in species protection, with a special focus on the Endangered Species Act of 1973. Prompted by the much-publicized Supreme Court decision in the "snail darter case"--TVA v. Hill-Congress extensively amended the Act in 1978. After a detailed analysis of these amendments, Professor Rosenberg …

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An Octic Reciprocity Law Of Scholz Type, Duncan A. Buell, Kenneth S. Williams Dec 1979

An Octic Reciprocity Law Of Scholz Type, Duncan A. Buell, Kenneth S. Williams

Faculty Publications

No abstract provided.

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Nonenzymatic Glucosylation Of Rat Albumin: Studies In Vitro And In Vivo, James F. Day, Robert W. Thornburg, Suzanne R. Thorpe, John W. Baynes Oct 1979

Nonenzymatic Glucosylation Of Rat Albumin: Studies In Vitro And In Vivo, James F. Day, Robert W. Thornburg, Suzanne R. Thorpe, John W. Baynes

Faculty Publications

Incubation of rat serum with D-glucose in vitro resulted in nonenzymatic glucosylation of serum proteins. Analysis of freshly isolated rat albumin by ion exchange chromatography indicated that the glucosylated albumin accounts for 6.7.+-. 0.9% of total albumin in normal rat serum. Glucosylation of rat albumin in vitro was 1st order with respect to glucose and albumin concentrations and occurs primarily (> 90%) at intrachain lysine residues. Kinetic analysis and inhibition of glucosylation by aspirin suggest that 1 reactive lysine residue is the primary site of glucosylation. Less than 5% of the radioactivity from glucosyl-albumin was released as glucose or mannose …

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Spin-Glass-Like Behavior In Very Dilute Pdfe At Very Low Temperatures, Richard A. Webb, G. W. Crabtree, J. J. Vuillemin Sep 1979

Spin-Glass-Like Behavior In Very Dilute Pdfe At Very Low Temperatures, Richard A. Webb, G. W. Crabtree, J. J. Vuillemin

Faculty Publications

Measurements of the electrical resistivity of palladium, residual resistivity ratio ∼22 500, containing 1.7 ppm of Fe have been made from 5.5 K to 1.8 mK. 15 Hz ac susceptibility measurements from 1 K to 1.8 mK together with the resistivity data suggest that a transition into a spin-glass state occurs near 7 mK.

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Enhanced Nonenzymatic Glucosylation Of Human Serum Albumin In Diabetes Mellitus, C. Earl Guthrow, Mary Ann Morris, James F. Day, Suzanne R. Thorpe, John W. Baynes Sep 1979

Enhanced Nonenzymatic Glucosylation Of Human Serum Albumin In Diabetes Mellitus, C. Earl Guthrow, Mary Ann Morris, James F. Day, Suzanne R. Thorpe, John W. Baynes

Faculty Publications

Use of an ion exchange chromatographic method and a colorimetric method with thiobarbituric acid showed that levels of nonenzymatically glucosylated serum albumin were increased in patients with poorly controlled diabetes mellitus compared to controls. The two methods correlated well (r = 0.99) and clearly discriminated between normal and poorly controlled diabetic populations. The levels of glycosylated hemoglobin were also measured in both populations. Several patients apparently in good control based on glycosylated hemoglobin measurements were found to have increased levels of glycosylated albumin. Because albumin has a shorter circulating half-life than does the human erythrocyte, the plasma concentration of glucosylated …

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Heating-Effect Minimization In Dye Lasers, Kenneth Lee Matheson, James M. Thorne Aug 1979

Heating-Effect Minimization In Dye Lasers, Kenneth Lee Matheson, James M. Thorne

Faculty Publications

Optical pumping of dye lasers deposits heat nonuniformly in the active medium. Because the refractive index of a liquid or gas is a function of temperature, gradients are created which refract the laser beam. This effect is sometimes serious enough to quench laser action. In this paper, we evaluate the effects caused by optical pumping with a coaxial flashlamp and suggest ultraviolet absorbers and wavelength shifters as materials for minimizing the problem

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Nonenzymatically Glucosylated Albumin: In Vitro Preparation And Isolation From Normal Human Serum, James F. Day, Suzanne R. Thorpe, John W. Baynes Feb 1979

Nonenzymatically Glucosylated Albumin: In Vitro Preparation And Isolation From Normal Human Serum, James F. Day, Suzanne R. Thorpe, John W. Baynes

Faculty Publications

Incubation of human serum with D-[6-3H]glucose resulted in the gradual accumulation of radioactivity in acid-precipitable material. Upon chromatography on Sephadex G-200, radioactivity was found associated with each of the major molecular weight classes of serum protein. Purified human serum albumin was also glucosylated in vitro upon exposure to D-[6-3H]glucose in phosphate-buffered saline. The glucosylated and unmodified albumins were separated by ion exchange chromatography. The physiological significance of these observations in vitro was confirmed by the isolation and quantitation of glucosylated albumin from normal human serum. Glucosylated albumin represents approximately 6 to 15% of total serum albumin in normal adults. The …

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Chemical Vapor Deposited Molybdenum Films For Use In Photothermal Conversion, David D. Allred, G. E. Carver, B. O. Seraphin Nov 1978

Chemical Vapor Deposited Molybdenum Films For Use In Photothermal Conversion, David D. Allred, G. E. Carver, B. O. Seraphin

Faculty Publications

High infrared reflectance, coupled with higher solar absorptance, is required for efficient photothermal conversion. Converters can be fabricated by depositing an absorber on a highly reflecting metal. The absorber functions in the visible, yet becomes transparent in the near infrared, allowing the metal to suppress the thermal emittance. Economic considerations demand the use of thin films, rather than bulk materials. The thin film reflector must be capable of withstanding high temperatures of operation. Compatibility of the reflector with the substrate below, and the absorber above, is required for long-time service. Highly reflective silver films suffer reflectance losses by agglomeration, and …

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Chemical Vapor Deposited Amorphous Silicon For Use In Photothermal Conversion, David D. Allred, D. C. Booth, M. Janai, G. Weiser, B. O. Seraphin Nov 1978

Chemical Vapor Deposited Amorphous Silicon For Use In Photothermal Conversion, David D. Allred, D. C. Booth, M. Janai, G. Weiser, B. O. Seraphin

Faculty Publications

Efficient photothermal conversion requires surfaces of high solar absorptance and low thermal emittance. This can be accomplished by the tandem action of a good infrared reflector overlaid by a film of sufficient solar absorptance that is transparent in the infrared. Crystalline silicon is a suitable candidate for the absorber layer. Its indirect band gap, however, results in a shallow absorption edge that extends to far into the visible. In contrast, the absorption edge of amorphous silicon is steeper and located farther into the infrared, resulting in a larger solar absorptance. We report on the fabrication of amorphous silicon absorbers by …

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An Emulsion Dye Laser, Kenneth Lee Matheson, James M. Thorne Nov 1978

An Emulsion Dye Laser, Kenneth Lee Matheson, James M. Thorne

Faculty Publications

A laser dye which is insoluble in water has been dissolved in hexane and emulsified in a water matrix. When pumped with a nitrogen laser, this mixture was observed to lase. The emulsion is superior to a simple hexane solution because the excellent thermo-optical properties of the water matrix help prevent refractive-index gradients from degrading laser performance. This is a useful characteristic for flash-pumped dye lasers, laser-pumped dye lasers, and liquid filters. Another type of solvent system, a critical solution, is also discussed. For certain dyes, a critical solution has even better thermo-optical properties because of its ability to absorb …

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[3H]‑Raffinose, A Novel Radioactive Label For Determining Organ Sites Of Catabolism Of Proteins In The Circulation, Jonathon Van Zile, Lee A. Henderson, John W. Baynes, Suzanne R. Thorpe Sep 1978

[3H]‑Raffinose, A Novel Radioactive Label For Determining Organ Sites Of Catabolism Of Proteins In The Circulation, Jonathon Van Zile, Lee A. Henderson, John W. Baynes, Suzanne R. Thorpe

Faculty Publications

The primary tissue sites of catabolism of plasma proteins with long circulating half-lives are unknown. It has been difficult to identify these sites because plasma proteins are delivered to tissues at relatively slow rates but are rapidly degraded intracellularly within lysosomes. Therefore, a tracer attached to protein is lost from the site of uptake before an amount sufficient for quantitation can accumulate. We hypothesized that sucrose (Glupal-2 /3Fruf) would be a useful label to circumvent this difficulty because of the stability of sucrose in lysosomes; and thus, sucrose should remain in tissue long after the protein to which it was …

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Bayes Estimation Of Reliability For Mixtures Of Life Distributions, William J. Padgett, Chris P. Tsokos Jun 1978

Bayes Estimation Of Reliability For Mixtures Of Life Distributions, William J. Padgett, Chris P. Tsokos

Faculty Publications

No abstract provided.

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Maximal Residue Difference Sets Modulo P, Duncan A. Buell, Kenneth S. Williams May 1978

Maximal Residue Difference Sets Modulo P, Duncan A. Buell, Kenneth S. Williams

Faculty Publications

Let p ≡ 1 (mod 4) be a prime. A residue difference set modulo p is a set S = {ai} of integers ai such that (ai/p) = +1 and ((ai - aj)/p) = +1 for all i and j with i ≠ j, where (n/p) is the Legendre symbol modulo p. Let mp be the cardinality of a maximal such set S. The authors estimate the size of mp.

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